| 摘要 |
Non-Imaging beam conditioning optical elements are disclosed which allow nearly full power usage from a light source, in a beam scanning information readout device such as a bar code reader. Light which would have been otherwise wasted by using stop apertures as in prior art scanning devices, is utilized efficiently by apportioning a greater amount of the light to the far out targets and less to the close in targets, effectively solving the problem of signal amplitude variation over a long working range. At the same time the novel optical elements provide multiple focal ranges which may be made to overlap thereby providing small beam cross sections for near and distant targets, significantly extending the depth of scanning range over prior art scanners. Amplification and signal processing of received light signals is simplified thereby eliminating the need for complex and fussy AGC amplifiers and limiters to deal with both strong and weak signals from close and distant targets respectively. Novel signal processing circuitry is also disclosed for adaptively processing received signals and for reducing variation associated with laser diodes, optical elements, and target related variables such as such as distance, reflectivity and contrast.
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